This invention relates in general to digital systems and more specifically to a system and method for allowing fast angle or scene changing in playback of video productions such digital versatile disc (DVD) playback devices.
Today's video playback systems often provide several new features. One feature, called “multi-angle,” allows a user to select a desired camera angle from which to view a currently displayed scene. For example, if a user is watching a music video and the user would like a close-up of the singer, instead of the currently presented medium shot, the user can depress a button on a remote control device and select the singer's close-up angle. A user can select a different scene or shot, entirely, such as requesting that a view of a guitar player, rather than the singer, be displayed.
Any number and type of angle (or other scene selections) can be made as long as they are within the performance ability of the video playback system and as long as they are provided by the video content. Additional content, such as audio, menu, sub-picture or other information, can also be the subject of angle or scene changes. For example, in the case where a user selects a shot of the guitar player, the audio track can be changed so that the guitar sound is louder in the audio mix.
Typically, today's playback systems limit the number of possible angles that can be selected by a user at any point in time. For example, up to 9 different angles are provided in a standard DVD-Video specification published by the DVD Format/Logo Licensing Corporation, entitled “DVD Specifications for Read-Only Disc/Part 3: Video Specifications, Version 1.13” that is hereby incorporated by reference as if set forth in full in this specification.
Another limitation of today's playback systems is that the angle switch is not instantaneous. Typically there can be anywhere from one-half to 6 seconds, or so, of delay after a user makes an angle change selection until the selected angle actually appears on a display screen.
This delay is due to a number of factors. One factor is the time required to “flush” or update various buffers and other components in the playback system to remove data relating to the deselected track and fill the buffers with data relating to the selected track. Depending on the speed of the system, and the number and size of the buffers, the updating of buffers can take several seconds.
Another factor in the delay is that the video information on the DVD is stored in compressed form, and includes other associated data (e.g., parity, error correction, channel assignment, header information, etc.). The DVD data must be decompressed, or decoded, and the associated data may require additional processing before the video information is made available in a format that is fit for display. The delay due to decoding and other processing can typically be about one-half of a second.